my grill will not stay lit?

Its probably a failed thermocouple or the flame not playing properly in the thermocouple tip.

Manual here: http://www.gotogasdocs.co.uk/boiler-manuals.php?i=Leisure_Cookers

Part here, but check it is the correct one fo ryour exact model oven:

http://www.espares.co.uk/search/mo1385162pt1863/cookers-and-hobs/thermocouples/leisure/cm101nrkp

XXX
January 2016